1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, to a semiconductor device having a transistor element and a rectifying element on a single substrate.
2. Description of the Related Art
Conventionally, there has been proposed a semiconductor device in which a transistor element and a rectifying element are formed on a single substrate. In the case where a rectifying element needs to be added to a single substrate on which a lateral field-effect transistor (FET) utilizing a two-dimensional electron gas layer is formed, a structure as illustrated in FIG. 13 can be considered (refer to, e.g., Patent Document 1).
As illustrated in FIG. 13, a semiconductor device 200 has a hetero junction 101 of nitride semiconductors disposed on a substrate 100. The hetero junction 101 is formed between a first nitride semiconductor 103 formed on the substrate 100 through a buffer layer 102 and a second nitride semiconductor 104 formed above the first nitride semiconductor 103. The first nitride semiconductor 103 has a two-dimensional electron gas layer at the vicinity of the hetero junction 101. A source electrode 105 and drain electrode 106 ohmic-contacting with two-dimensional electron gas are provided on the second nitride semiconductor 104. A gate electrode 107 is formed on the second nitride semiconductor 104 at a portion between the source and drain electrodes 105 and 106. A Schottky electrode 108 Schottky-contacting with the second nitride semiconductor 104 is formed on the second nitride semiconductor 104 at a portion on the opposite side to the gate electrode 107 with respect to the drain electrode 106. As described above, a rectifying element 109 having the Schottky electrode 108 as the anode electrode and drain electrode 106 as the cathode electrode is formed, whereby the semiconductor device 200 having the transistor element 110 and rectifying element 109 on the single substrate 100 is formed.
In the case where a high-voltage and high-speed GaN based semiconductor device is produced, in order to allow the semiconductor device to operate at high speed, it is preferable to make the anode electrode have a Schottky barrier diode (SBD) structure using a Schottky electrode suitable for high-speed operation.